In recent years, disk devices such as magnetic disk drives and optical disk drives have widely been used as external storage devices and image recording devices of computers.
As such a disk device, for example, a magnetic disk drive generally comprises a magnetic disk provided in a case, a spindle motor which supports and rotates the magnetic disk, and a suspension assembly which supports a magnetic head. The suspension assembly includes a suspension attached to a distal end portion of an arm, and a trace member (a flexure or a wiring trace) provided on the suspension. The trace member includes a gimbal portion which supports the magnetic head.
In more recent years, there is proposed a suspension assembly wherein thin piezoelectric elements (PZT elements) serving as actuation elements are mounted in the vicinity of a gimbal portion of a trace member, and a magnetic head is minutely displaced in a seek direction by expansion and contraction of the piezoelectric elements. According to the suspension assembly, the operation of the magnetic head can be minutely controlled by controlling a voltage to be applied to the piezoelectric elements.
In the suspension assembly, each PZT element is fixed by its entire surface to a base insulating layer of the trace member. But the PZT elements are very small, and consequently a very high precision adhesion process is required. More specifically, if control of the amount of adhesive applied is insufficient, a PZT element may become detached, or the adhesive may ooze or flow out around an inappropriate region. Further, if preliminary curing of the adhesive is not carried out properly, a PZT element may be left floating or the like. In this case, it is difficult to stably transmit the driving force produced by the expansion and contraction of the piezoelectric elements to the trace member. As a result, the stroke is decreased and the dispersion of the stroke increased.